#define _USE_MATH_DEFINES
#include<iostream>
#include<vector>
#include<algorithm>
#include<cmath>
#include<string>
#include<iomanip>
#include<numeric>
#include<queue>
#include<deque>
#include<stack>
#include<set>
#include<map>
#include<random>
using namespace std;
typedef long long ll;
const int mod=998244353;
int main(){
	double a,b,x,y;
	cin>>a>>b>>x>>y;
	cout<<fixed<<setprecision(20)<<min(x/a,y/b)*(a+b)<<endl;
}